This book includes peer-reviewed articles from the National Conference on Advanced Instrumentation for Nuclear Physics, High-Energy Physics, and Medical Imaging-2026, held on 23–25 February at Gaya, India. It provides a comprehensive overview of the latest research trends and advancements across detector technology and medical imaging. It highlights cutting-edge developments in advanced detector technologies and materials, drawing insights from high-energy and nuclear physics to enhance medical performance. This book covers the progress achieved by advanced detector design & characterization, computational simulations, and sophisticated  image reconstruction image reconstruction. This volume bridges the gap between fundamental science and societal application, highlighting how advanced detector technology developed for nuclear and high-energy physics is actively reshaping medical science.